This invention relates generally to a transport system for elongated sheet material and, more particularly, to such a system for feeding such material along a fixed longitudinal axis.
There exist many types of sheet material feed apparatus that include regulation systems for maintaining the traveling sheet material on a fixed longitudinal axis. Typically, the regulation systems comprise one or more sensing devices that determine dynamically the lateral position of at least one longitudinal edge of the traveling sheet. The sensing device determines whether the observed position of the longitudinal edge complies with the longitudinal alignment requirements for the traveling sheet material. Depending upon the particular sheet material being handled and other operating conditions, the sensors can include photosensitive detectors, pressure change detectors, mechanical feelers, etc. In response to an output from the sensing device indicating an unacceptable lateral displacement, a positioning mechanism is actuated to realign the traveling sheet. Prior positioning devices have includes, for example, servo mechanisms for axially shifting a supply roller from which the sheet is being drawn, mechanisms for controlling the tilt of transport drive rollers, and mechanisms for producing axial translation of drive rollers. All such prior positioning devices suffer collectively or individually from a number of deficiencies such as being complicated, expensive, unreliable, etc. Also known are positioning devices that maintain desired alignment by spreading or stretching a sheet material. These latter systems obviously are unsuitable for use with nonstretchable sheet material such as paper and metal.
The object of this invention, therefore, is to provide an elongated sheet transport and guidance system that combines the features of simplicity, inexpensiveness and reliability.